Season the chops on both sides with salt and pepper. Heat the oil in a shallow flameproof casserole with a tight-fitting lid and fry the chops for 5 minutes until browned on both sides.
Scatter the onions into the casserole and add the oregano, lemon rind and juice and cinnamon. Tuck the tomatoes and potatoes around the lamb and add the stock and a little salt and pepper.
Cover and bake in a preheated oven, 160°C (325°F), Gas Mark 3, for 2 hours or until the lamb is very tender. Serve with warmed Greek bread.